Dozens dead in 'US-led strike' in Syria's al-Mayadeen

A suspected US-led coalition air raid on an ISIL-run prison in easternSyriahas killed at least 57 people, according to a monitoring group.

TheSyrian Observatory for Human Rightssaid on Tuesday that most of the dead in the town of al-Mayadeen in Deir Az Zor province were civilian inmates.

At least 15 ISIL fighters were also killed in the raid, said the UK-based monitor, which tracks developments in Syria's long-running conflict via a network of contacts on the ground.

Al-Ikhbariya, aSyrian state-run TV station,also cited its Deir Az Zor correspondent as saying coalition fighter jets had destroyed a building in al-Mayadeen used as a prison byISILto hold a "large number of civilians".

An activist-run media outlet in Deir Az Zor also reported the hit, which it said took place at dawn on Monday.

The US Central Command confirmed to the Associated Press news agency on Tuesday that it struck ISIL facilities in al-Mayadeen on June 25 and 26, but made no direct reference to the alleged ISIL prison.

CENTCOM saidit would assess the allegations that civilian prisoners were killed, andit would publish the results of its assessment in its monthly civilian casualty report.

It said the Mayadeen mission was "meticulously planned and executed to reduce the risk ... to non-combatants".

The US-led coalition is supporting an alliance of Kurdish and Arab fighters in their assault on ISIL in its de facto capital of Raqqa in northern Syria.

"The removal of these facilities disrupts ISIS's ability to facilitate and provoke terrorist attacks against the coalition, our partner forces and in our homelands,"Colonel Joe Scrocca, coalition director of public affairs, said in an email to Reuters news agency.

ISIL is believed to have moved most of its leadership to Mayadeen, southeast of Raqqa, according to US intelligence officials.

Among operations reportedly moved to Mayadeen, about 80km west of the Iraqi border, are its online propaganda operation and its limited command and control of attacks inEuropeand elsewhere, they said.